Volcanoes p.p. --one to use


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Volcanoes p.p. --one to use

  1. 1. Introduction to volcanoesVolcano: an opening in the earth’s surface through which lava, hot gases, and rock fragments erupt
  2. 2. Origin of Volcanoes1. Magma 50-100 miles below the earth’s surface slowly begins to rise to the surface2. As the magma rises it melts gaps in the surrounding rock3. As more magma rises a large reservoir forms as close as 2 miles below the surface (magma chamber)
  3. 3. Origin of Volcanoes4. Pressure from the surrounding rock causes the magma to blast or melt a conduit (channel) to the surface where magma erupts onto the surface through a vent (opening)
  4. 4. Origin of Volcanoes5. The magma, now called lava, builds up at the vent forming a volcano
  5. 5. Origin of Volcanoes6. Often the volcano sides will be higher than the vent forming a depression called a crater
  6. 6. Crater:
  7. 7. Caldera: an unusually large crater or the remains when the cone collapses into its own magma chamber
  8. 8. Anatomy of a VolcanoCone: the above ground structure built from lava and/or tephra
  9. 9. Conduit: the path that magma takes from the magma chamber to the vent
  10. 10. Magma Chamber: the reservoir located under the volcano where magma collects and becomes the supply of magma/lava to build the volcano
  11. 11. Parasitic Cone: a smaller secondary volcano built on the side of or near the main volcano, but sharing the same conduit to the magma chamber
  12. 12. Fumarole: a secondary vent that emits only gases
  13. 13. Fissure: a long fissure (crack) from which lava flows
  14. 14. Vent: opening of the volcano, through which lava, ash and gases flow
  15. 15. Take a minute tolabel the parts onthe diagram (not all parts are shown)
  16. 16. Crater Ash Cloud/Gases VentParasitic Cone Lava Flow conduit mantle Magma chamber
  17. 17. Lava— There are 3 kinds:
  18. 18. Pahoehoe lava: Hot, thin, fast flowing harden with a relatively smooth surface Often has a ropy or wrinkled appearance
  19. 19. Pahoehoe lava:
  20. 20. Aa lava:• Cooler, thicker, slow moving• Hardens with a rough, jagged, sharp edge surface
  21. 21. Pillow Lava: Lava suddenly cooled by water shows sack-like segments (stuffed pillows)
  22. 22. Can you identify the kindsof lava from the pictures? Circle your choice.
  23. 23. Tephra (pyroclastic, rock fragments) Volcanic Dust: Smallest particles and carried by atmosphere circulation
  24. 24. Volcanic Ash: 0.25-0.5 cm diameter Generally settles out within miles of the cone but can be carried greater distances by stronger winds. Forms a mudflow when mixed with water
  25. 25. Bomb: Smaller bombs (gravel, pea size) are called cinders. Walnut size bombs are called lapilli. Larger fragments up to 4+ feet in diameter are called bombs.
  26. 26. Lahar (mudflow): mixture of ash, eroded land, and water flowing down river valleys
  27. 27. Lahar (mudflow):
  28. 28. Gases: water vapor, carbon dioxide, nitrogen, sulfur dioxide, hydrogen sulfide, chlorine
  29. 29. Locations of VolcanoesDivergent Boundaries: As the plate move long cracks (rifts) form and lava builds up forming volcanoes.
  30. 30.  If the boundary is on the ocean floor, volcanoes can grow tall enough to break the surface of the ocean and become islands (Iceland)
  31. 31. Convergent Boundaries: Places where plates are moving toward each other forming a subduction zone. One plate melts under the other and the magma moves upward to form volcanoes.
  32. 32.  Example: Pacific Ring of Fire
  33. 33.  Example: Cascade Volcanoes
  34. 34. Hot Spots Magma that may originate in the mantle or outer core will move upward, breaking the surface and forming a volcano, they are independent of plate boundaries and a chain of volcanoes may form as the plate moves across a hot spot.
  35. 35. Hot Spots (Examples: Hawaiian Islands and Yellowstone National Park)
  36. 36. Types of Volcanic Eruptions Two factors determine the type of eruption: Amount of water vapor & other gases in the magma The chemical composition of the magma
  37. 37. Explosive Eruptions Trapped gases under high pressure will violently explode when the magma reaches the lower pressure of the surface. Has granitic magma is very thick and plugs the vent causing the pressure to build until it blows violently out the vent The high water content of the magma produces more water vapor which when mixed in granitic magma produces explosive eruptions
  38. 38. Explosive EruptionsMt. Pinatubo Mont serrat Mt. St. Helens
  39. 39. Quiet Eruptions Low pressure gas Has basaltic magma (is more fluid and will flow instead of explode) And has low water content
  40. 40. Types of Volcano MountainsCinder Cones: Small base, steep-sided, loosely consolidated Up to 1000 feet tall Life span of a few years Commonly built from gravel size lava rock fragments call cinders Has violent eruptions, dangerous when close.
  41. 41. Types of Volcano MountainsCinder Cones:
  42. 42.  High pressure gas bubbles cause thick lava to explode into the air; lava begins to cool as it rises and falls, becoming very sticky When lava hits the ground it sticks rather than flows This builds a steep cone with a small base
  43. 43. Sketch a Cinder Cone Volcano:
  44. 44. Types of Volcano MountainsShield Volcanoes: Large base, gentle slope, lava rock layers A few miles wide Life span of a million years or more The lava is hot, thin, very fluid, often basaltic. Example: Hawaiian Islands
  45. 45. Take a look at these examples:http://www.volcano.si.edu/world/tpgallery.cfm?category=Shield%20Volcanoes The Mauna Loa volcano in Hawaii— the largest volcano on Earth—has the broad expanse characteristic of shield volcanoes. It spreads across half the island of Hawaii. Shield volcano on Mars; Taken from space
  46. 46. Shield Volcanoes Mauna Kea
  47. 47. Sketch a sheild Volcano:
  48. 48. Types of Volcano MountainsComposite (strato) Volcanoes: Large mountain volcano often snow capped, a few miles high Life span of million years or more Have alternating eruptions of tephra (air- borne) and lava. The tephra adds height to the volcano and the lava cements the tephra together and adds to the base. Found mostly in subduction zones and have violent eruptions.Examples: Mt Rainier, Mt Fuji, Mt Kilimanjaro
  49. 49. Composite (strato) Volcanoes: (Make a Flip-Book) Mt. FujiMt. Rainier Mt. Kilimanjaro
  50. 50. Sketch a composite Volcano:
  51. 51. Volcano Activity Levels (Stages)Active (awake): Has erupted within recent time and can erupt again at any time.Pre-eruption activities:  Increase in earthquake activity under the cone  increase in temperature of cone,  melting of ice/snow in the crater  swelling of the cone  steam eruptions  minor ash eruptions
  52. 52. Mt St. Helens
  53. 53. Dormant (sleeping): No eruption within recent times, but there is record of past eruptions Can become active and erupt again after a “wake up” period Example: Mt. Rainier
  54. 54. Extinct: No eruption within recorded history Not expected to ever erupt againExample: Mount Mazama (Crater Lake)
  55. 55. Crater Lake
  56. 56. Mount Rainier • The most dangerous volcano in the US • The danger is mostly from lahars traveling down river valleys at a speed of 25mph and destroying everything in its path • 100,000 people live on the solidified mudflows of previous eruptions
  57. 57. Mount Rainier • The mountain is dangerously unstable, a tall, steep heap of loose rock held together by the force of gravity and a cubic mile of glacier ice that could be melted or shaken loose • Lahar flows average every 500 years and have gone as far as the Puget Sound lowlands (1 in 7 chance of it happening during your lifetime) • Mount Rainier has erupted 4 times in the last 4000 years with the last eruption 200 years ago
  58. 58. VolcanoVideos• http://video.nationalgeographic.com/video/player/ environment/environment-natural- disasters/volcanoes/volcano-eruptions.html• http://video.nationalgeographic.com/video/player/ environment/environment-natural- disasters/volcanoes/volcano-lava.html• http://video.nationalgeographic.com/video/player/ environment/environment-natural- disasters/volcanoes/volcano-eruptions.html